Folding of sheets of material (e.g., paper, napkins, paper towels, tissue, etc.) is frequently performed using a pair of folding rolls that have interacting mechanical gripper and tucker assemblies. The gripper and tucker assemblies are uniformly spaced around a circumference of each respective folding roll to interact with one another so as to interfold the sheets of material. The tucker assemblies on one roll interact with the gripper assemblies of the adjacent roll, and vice versa, to alternately grip and tuck successive sheets of material fed between the rolls. As the rolls rotate, the gripper assemblies carry and release the folded sheets of material to create a zigzagged interfolded stack of sheets.
However, known gripper assemblies have several drawbacks. For example, known gripper assemblies utilize a shaft that is rotatably mounted to the roll using a series of spaced apart exposed bushing assemblies, all of which requires periodic lubrication. Furthermore, each folding roll includes a number of shafts, each of which is mounted using a number of such bushings, and each bushing constitutes a component that is subject to wear and potential failure and replacement. The folding roll operates in an environment in which the bushings are subject to introduction of contaminants, which can reduce shaft/bearing life and increase the torque required to rotate the shaft. Furthermore, the shaft of a gripper assembly of this type requires extensive low tolerance machining to assemble. Because of this machining requirement, it is not possible to use a hardened steel material for the gripper assembly shaft.
It is the object of the present invention to provide a gripper assembly for an interfolding machine that overcomes these shortcomings of the prior art.